Adding type signatures to `#audit_formula` methods in formula cops
would lead to verbose, repetitive signatures across the existing ~63
instances. This reworks `#audit_formula` to use a `T::Struct` for its
arguments, which allows us to use a one-line signature for these
methods.
- Ensure that new formulae problems aren't duplicated
- Now that homebrew/core will imminently not have options adjust the
various audits so they make more sense (and exclude taps)
- Exclude taps from more preferential audits
